Tuesday, January 25, 2011

In physics, matter is the stuff that everything is made of, but let’s explore that, shall we? Take a pencil, for example. It’s made of wood for the most part. But what is wood made of? The main component of wood is the organic compound cellulose, composed of carbon, hydrogen and oxygen which forms very long chain molecules. It’s organic because it contains carbon, but what is carbon made of?

Carbon is the element in chemistry with atomic number 6. One atom of carbon has six protons, six electrons and either six, seven or eight neutrons which make up the three isotopes of carbon: carbon-12, carbon-13 and carbon-14, respectively. The nucleus of the carbon atom is composed of the protons and neutrons tightly held together by a strong nuclear force. The six electrons orbit the nucleus, creating an “electron cloud” and held within this cloud by an electromagnetic force that exists between the electrons and protons. Drilling down further, lets look at the proton. Protons are subatomic particles with an elementary electric charge of +1 that live in the nucleus along with neutrons. The number of protons in the nucleus is the defining characteristic of an element. Hydrogen, the lightest element, has but a single lonely proton and therefore is said to have an atomic number of one. Element 118, known as ununoctium, has the highest number of protons in its nucleus, but it’s highly unstable. Only three or four atoms have been produced and detected.

But what is a proton made of? Can we drill down farther? Protons are composed of yet smaller fundamental particles called quarks: two “up” quarks, each with a charge of +2/3 and one “down” quark, with a charge of -1/3. Quarks are exceedingly small and cannot exist in isolation, so much of what we know about them is inferred by observing the various particles they form. The name quark comes from the line in Finnigan’s Wake “Three quarks for Muster Mark!” which is fitting since they like to hang out in threes.
There have been attempts to drill down further still. String theory asserts that quarks and electrons are made up of 1-dimensional vibrating strings. String theory requires the existence of extra dimensions beyond the normal four dimensions of space and time, although the precise number of dimensions is up for debate. The most popular variant of string theory, called M-theory, requires 11 spacial dimensions where the strings are cross sections of 2-dimensional vibrating membranes. The main problem with string theory, though, is that it doesn’t put forth any predictions which can be tested. Until it does that it will belong more to the realm of math or philosophy than the world of science.

1) True or false: Atomic number is controlled by the number of particles in the nucleus.

Monday, January 10, 2011

Last week we discussed how vitally important it is to have liquid water on a planet’s surface in order to support life. But there is another possibility—another route to life might exist.
Europa, Jupiter’s 6th moon, is slightly smaller than our moon and is covered in ice. But what is really unusual is how smooth its surface is—very few craters and mostly covered with streaks and cracks. This has led scientists to hypothesize that beneath all that ice are oceans of liquid water. Europa receives very little energy from the Sun, so how does it generate enough heat to keep its oceans from freezing solid? It turns out that Jupiter interacts with its moons Io, Europa and Ganymede in such a way as to distort their orbits into more elliptical shapes, and this causes tidal flexing which heats Europa’s interior similar to how squeezing a ball of clay will heat it slightly. The question is whether this is enough to give Europa a liquid ocean of water under its icy crust.
Assuming Europa does have liquid water, what is the chance that it might also have life? We might be closer to answering that question than one would think. Surprisingly, there is a place here on Earth that has similar conditions: Lake Vostok. Lake Vostok is a subglacial lake located 4,000 meters below the surface of Antarctica and has more fresh water than Lake Eerie and Lake Ontario combined. It has been isolated from the rest of the world for 14 million years and there is a team of Russian scientists that have been drilling through the ice off and on since 1990 and they are currently within 100 meters of breaking through the ice. Once through, they will sample the water with the hope of finding extremophiles—organisms that thrive in extreme environments. If they do find life, it will reinforce the case for extraterrestrial life and no doubt help shape theories on the nature of life in our universe.

1) True or false: Lake Vostok is the largest subglacial lake on Earth.

2) Which of the following is not one of Jupiter’s moons?
a) Ganymede b) Titan c) Io d) Europa

3) True or false: an organism that thrives in severely hot or cold environments would be called an extremophile.

Tuesday, January 4, 2011

Sunday, January 2, 2011

A Goldilocks planet is one with conditions that are “just right” to sustain life. It must fall within a star’s habitable zone—neither too far nor too close from its star so that water can exist in liquid form on its surface. It also needs to be large enough with enough gravity to keep an atmosphere. Gravity is incredibly weak—our whole Earth doesn’t have enough gravitational pull to stop you from picking up a pebble. Yet it is enough to keep our atmosphere in place. The Moon, being only a fraction of Earth’s mass, doesn’t have enough gravity to hold an atmosphere. And without an atmosphere, liquid water can’t exist—it will just boil away into space. We also rely on our atmosphere to protect us from ultraviolet radiation and meteorites. Without it we would be cooked and pummeled, again, just like the Moon.

Sunset as seen on Mars through its thin atmosphere.

The Earth’s liquid iron core generates a magnetic field which also protects us. This magnetosphere deflects solar winds that would otherwise strip us of our atmosphere. Mars, being much smaller than Earth, lost its magnetic field when its iron core cooled and as a result lost most of its atmosphere as well.

Yet having an atmosphere does not a guarantee life either. Take Venus for example. Its atmosphere is the product of a runaway greenhouse effect. Its ocean’s boiled away from the heat and volcanic activity has left it an atmosphere that is mostly carbon dioxide. As a result, the planet that most closely resembles Earth is so hot that lead would melt on its surface.Goldilocks planets are of key interest to researchers looking for intelligent life or for a future home for the human race. Finding Goldilocks planets is an important part of the Kepler Mission (more here), which uses a space telescope to survey and compile the characteristics of such planets.

1) True or false: Mars is a Goldilocks planet.

2) Which of following is not true about our atmosphere?a) without it, we could not have liquid water b) it protects us from ultraviolet radiation c) it deflects solar winds d) it protects us from meteorites

3) True or false: having an atmosphere guarantees that a planet can have liquid water.